Project Summary Attention is the gateway to all we perceive, learn and remember, and disorders of attention continue to be a national public health concern. Although we live in a world of overlapping, dynamic, multimodal events, little is known about the development of attention in the context of this complexity. Infants must learn to selectively attend to unitary multimodal events (intersensory processing, IP) by detecting synchronous sights and sounds (e.g., face and voice of a speaker) and to flexibly shift and maintain attention in the context of competing stimulation. These basic skills, which we call ?multisensory attention skills? (MASks), provide a cornerstone for language and social development. However, there is no systematic database characterizing the early typical development of these foundational MASks or the developmental pathways through which they lead to optimal outcomes. A key obstacle to progress has been the lack of individual difference measures appropriate for infants and children. To address these issues we have created the first individual difference protocols for assessing MASks, and will use them here to build the first developmental database (across 3-72 mos), and to model developmental pathways from MASks to critical child outcomes that rely on this foundation. Our measures index IP, attention maintenance, and shifting in the context of overlapping audiovisual social and nonsocial events at a grain of analysis needed for characterizing the proficiency of individual children, developmental change, and risk for atypical development. In my current R01, we are collecting longitudinal data for 107 infants across 3-36 mos using these protocols. Preliminary results show clear developmental change and impressive relations with language and social outcomes. Here, we build on these findings by testing: a) the same children at 48, 60, and 72 mos, b) a new cohort at 48, 60, and 72 mos, c) outcomes in two new domains critical for successful childhood functioning?self-regulation/EF and school readiness, and d) neural correlates of IP using ERPs. Using cutting-edge SEM-based growth curve and panel modeling, we will model how infant MASks develop and cascade to these important domains in childhood. The specific aims of this project are to characterize the typical longitudinal growth of MASks and define values signifying risk for delays (Aim 1), test models characterizing pathways from MASks to language and social competence (Aim 2), and to self-regulation/EF and school readiness (Aim 3). The larger sample at 48, 60, and 72 mos will enable us to test hypothesized and alternative models of developmental pathways in greater detail, assess practice effects and explore neural correlates of IP. Findings will advance theory and methodology by providing the first tools, data, and knowledge base of developmental processes through which basic MASks impact important outcomes in childhood. This has potential to catalyze a shift in the study of multisensory attention in line with the current shift in developmental science, focusing on individual differences and developmental change?a level of analysis necessary for identifying atypical development and guiding interventions.